1. Field of the Invention
The present invention relates to a grommet and more specifically a grommet that is externally fitted and fixed to a wire harness, the wire harness being arranged in an automobile, and placed in a through hole of a vehicle body in order to achieve protection of the wire harness, waterproofing, dust-proofing, and sound insulation. In particular, the present invention relates to a grommet that is prevented from deforming due to contact with an end of a corrugated tube which is continuous with the grommet and in which the wire harness is sheathed and is prevented from being placed at a tilt in a vehicle body panel.
2. Description of the Related Art
Conventionally, a wire harness arranged in a back door of an automobile is led out from a through hole provided in the back door and routed to a through hole of a vehicle body.
As shown in FIG. 8, that region of a wire harness which is routed from a through hole H1 of a back door 100 to a through hole H2 of a vehicle body 110 is sheathed in a grommet 120 made of a rubber or an elastomer, and vehicle body engagement portions 121 and 122 that are provided at respective ends of the grommet 120 are internally fitted to and engaged with the through holes H1 and H2 on the respective sides (see JP 9-92062A and JP 2008-230352A).
Specifically, the vehicle body engagement portion 121 of the grommet 120 is formed by providing a truncated cone-shaped tube portion 126 having an elliptical shape that is continuous with a leading end of a bellows-like tube portion 125, and providing an annular engagement groove 127 in an outer circumferential surface of a circumferential wall 126b extending from the outer circumference of a bottom wall 126a of the truncated cone-shaped tube portion 126.
When inserted and fixed into the through hole H2 of the vehicle body 110, the vehicle body engagement portion 121 is pushed into the through hole H2 from a leading end of the circumferential wall 126b, and fixed to the vehicle body 110 by a circumferential edge of the through hole H2 being inserted into, and thus fitted in and engaged with the engagement groove 127.
The wire harness that is routed through the through hole H2 of the vehicle body 110 and arranged in the vehicle body side is usually sheathed in a corrugated tube 130, which is a resin molded product, as shown in FIG. 9. There are cases where a leading end 130a of the corrugated tube 130 is inserted into the inside of the truncated cone-shaped tube portion 126 of the vehicle body engagement portion 121 of the grommet 120 and comes into contact with the circumferential wall 126b and the bottom wall 126a, pushing up and deforming the circumferential wall 126b. 
If the circumferential wall 126b of the vehicle body engagement portion 121 deforms as described above, the engagement groove 127 provided in the outer circumference of the circumferential wall 126b may also deform and thus the grommet 120 be attached at a tilt to the through hole H2 of the vehicle body 110. In this case, a certain portion of the entire circumference of the engagement groove 127 does not accurately fit flush with the circumferential edge of the through hole H2, and in this portion, a gap is left between an inner circumferential surface of the through hole H2 and an outer circumferential surface of the engagement groove 127. There is a risk that water may leak into the inside of the vehicle body through this gap, and the leaked water move through spaces among the wires constituting the wire harness to reach a connector (not shown) that is connected to a leading end thereof, causing a short circuit between terminals in the connector.
The invention has been made to solve the above-described problem, and it is an object thereof to enable a vehicle body engagement portion of a grommet to be placed in a through hole of a vehicle body without leaving a gap therebetween and to prevent the occurrence of a water leak, by preventing the vehicle body engagement portion from deforming even if a leading end of a corrugated tube is inserted into and comes into contact with the inside of the vehicle body engagement portion of the grommet when a wire harness is sheathed in the grommet and the wire harness leading out of the grommet is sheathed in the corrugated tube.